Currently, instruments such as drills, cutters and saws, which are inserted in the chuck of a medical handpiece, are mostly used in medicine for removing tissue. Sometimes, laser systems are used which can separate and/or remove soft and hard tissue.
In tissue removal, tissue cuts, tissue openings and tissue cavities or passageways are produced which should satisfy medical criteria (e.g., residual tissue is free of tumors, bacteria, caries, or the residual tissue has a high firmness) and/or additional criteria (e.g., the geometry of the removed tissue has a particular fitted shape for inserting a mating piece).
Coordinate measurement systems that can be used to measure the position (position and orientation) of a tool relative to a reference coordinate system are known from measurement technology.
Medical navigation systems are known from computer-assisted surgery which enable to display the position (position and orientation) of the instrument relative to a patient's tissue after registration of the tissue.
Medical robot systems are also known from robot-assisted surgery whereby the instruments can be moved by a robot on predefined pathways, so that for example a bore can be placed at a certain position (position and orientation) and a cavity with a particular geometric shape can be bored.
In addition, medical interactive systems are known from robot-assisted surgery, wherein the instruments are attached to a passive (actively braking) or to an active (actively driven) mechanism. However, a physician is able to move the instruments manually by directly guiding the instrument or the mechanism inside specified volumes, on specified surfaces and along specified pathways (straight lines, curves), in order to place, for example, a bore at a certain location (position and orientation) or to rebore a cavity with a particular desired geometric shape.
Moreover, medical tele-manipulation systems are known from robot-assisted surgery, whereby the instruments are attached to an active mechanism (slave manipulator), with a physician being able to move the instruments manually via a coupled input mechanism (master manipulator) inside specified volumes, on specified surfaces and along specified pathways (straight lines, curves), in order to place, for example, a bore at a certain location (position and orientation) or to rebore a cavity with a particular desired geometric shape.
Hand scanners, which are able to measure a 3-D-surface model with high accuracy via a streak projection or by other methods, are known in dentistry. A physician has been unable until now to use a manually guided instrument for removing tissue, so that the position and/or the geometry of the removed tissue corresponds precisely to predefined or dynamically specified medical criteria (e.g., the residual tissue is free of tumors, bacteria, caries, or the residual tissue have a high firmness) or geometric criteria (e.g., the residual tissue or the removed tissue has a particular fitted shape for inserting an object).
This is related to the observation that humans lack the ability to precisely orient their hands in a 3-D-reference coordinate system.
Even when using a navigation system, a physician has until now been unable to remove tissue with a manually guided instrument so that the position and/or the geometry of the removed tissue precisely corresponds to predefined or dynamically defined medical criteria (e.g., the residual tissue is free of tumors, bacteria, caries, or the residual tissue has a high firmness) or geometric criteria (e.g., the residual tissue or the removed tissue has a particular fitted shape for inserting an object).
Non-tactile tissue-removing effectors, such as laser beams, don't allow a user who manually treats hard tissue to detect by feel the shape of the removed tissue or the generated fitted shape. Fitted shapes (e.g., cylindrical) that satisfy certain criteria can therefore not be manually produced.
Robot-controlled, tele-manipulated or interactively robot-guided instrument inserts always significantly increase the complexity of the device which adds to its cost.
In addition, the attending medical personnel as well as the nursing staff must have a high level of training and motivation, requiring significant expenses for training and installation. The surgery often takes longer than without the use of a robot.
The patients have to be placed in a immobile position so as to achieve the desired precision when using a robot.
In dentistry, adjoining structures are frequently accidentally injured with a tissue-removing sensor and/or instrument. Even with navigation support, it is not always possible to cleanly shape a cavity. Prefabricated implants cannot be cleanly fitted. It is not possible to prefabricate inlays, onlays or bridges for a later fit. It is not possible to prefabricate a supra-construction so that it later fits perfectly. It is not possible to use high-quality standard inlays, onlays or bridges which are produced by a manufacturer of implants or similar manufacturers. It is not possible to cleanly reshape cavities so that they meet certain medical criteria (e.g., distance from bacteria-infected, tumorous tissue). It is not possible to cleanly reshape cavities so that they meet certain manufacturing criteria (e.g., shaping of the fitted piece for fabrication with three-axes cutters). It is not possible to cleanly reshape cavities so that they meet certain criteria for the integration of fitted pieces (insertion, plug-in, secured against rotation). It is not possible to cleanly reshape cavities so that they meet a combination of these criteria. It is not possible to measure and store manually removed tissue (e.g., on a model), and to use the removed tissue as a “template” for a tissue removal with identical shape on the same or on another object (e.g., a patient's tissue).
In soft tissue surgery cuts cannot be placed so as to correspond to certain medical criteria (e.g. distance to bacterial, tumorous tissue) and/or criteria for integrating transplants and implants (e.g., breast implants after tissue removal).
In knee endoprosthesis, multiple cuts cannot be produced without fixing or kinematic guiding with cleanly defined cut surfaces.
In spinal surgery, decompressions and pedicle screw insertion cannot be performed without fixing the tissue and/or kinematically guiding the instruments.
Another disadvantage of conventional solutions is that the navigation systems according to the state of the art cannot use tools whose transformation matrix is not known ahead of time. This limits the user to a tool set from a particular company. The user is unable to calibrate a new tool without problems. At least the push of a button is needed for calibration. If the tools of an instrument, such as for example a handpiece, are changed, there is a risk that an unregistered tool is being used. This can results in injury to the patient, since the position and angle values can be in error without being recognized as erroneous.
Handpieces, in particular for computer-assisted dentistry, are described in various publications. Two methods currently exist in dentistry which require marking the handpiece for a three-dimensional reference, namely on one hand manual drilling with navigated position orientation and, on the other hand, drilling with a kinematic mechanism, e.g. a robot.
U.S. Pat. No. 4,824,367 describes the device for displaying the parallel alignment of a dental handpiece, consisting of an angle sensor for generating electrical angle signals which indicate the orientation of a cutter that is operated with a dental handpiece, adjusting elements for adjusting electrical reference signals which indicate the position of a preset axis, warning elements which emit warning signals if the angle signal is outside a preset range.
U.S. Pat. No. 5,017,139 describes the device with a dental/medical surgical tool for obtaining three-dimensional contour information, consisting of a plurality of arm segments which are connected with each other sequentially, producing a structure with a front and a rear end, a first attachment element for attaching the first end of the structure to a stationary platform and a second attachment element for attaching a surgical tool at the second end of the structure, a plurality of encoders, whereby each encoder is connected with a corresponding arm segment, to produce an electric signal which displays the position of the individual segments. In this way, the position of the surgical instrument can be continuously tracked.
U.S. Pat. No. 6,000,939 describes a device for precise alignment of dental drills consisting of orientation elements for attachment to a dental handpiece, which generate a signal of the drilling angle, and comparison elements which emit warning signals, if the difference of the angle signals is located outside a predetermined range.
EP 0 741 994 A1 describes a method for visualizing the jaw of a person which includes the following steps: insertion of a device with markers for position measurements into the buccal cavity of the person; acquiring at least one image of the jaw with an imaging method, wherein the markers are also imaged, identification of the markers, wherein for visualization the following acts are performed: attaching a 3-D sensor on the outside of the respective jaw; renewed insertion of the position measurement device in the buccal cavity in the same position as during the acquisition of the image, if the device was removed in the meantime, wherein the device is provided with a 3-D sensor; determining the positional relationship between the 3-D sensor of device and the 3-D sensor on the outside of the jaw; removing the device for position measurements, generating a superposition of the optical image of the jaw with the data set in the proper positional relationship. Truppe describes the method also for visualizing a model of the jaw and/or for visualizing the model of the jaw and the jaw. Truppe also describes a method for visualizing the jaw or a model of the jaw, whereby in addition a photographic or video image of the jaw or of the model is produced, which is superimposed with the image obtained with the imaging method.
Ultrasound, optical or mechanical sensors can be used.
U.S. Pat. No. 5,688,118 describes a system for training dentists to produce cavities in teeth. A human phantom torso is placed in a dentist's chair with a model jaw. The student works with a special training units having a pneumatically driven drill and a handpiece which differ in their configuration and operation or application from a “genuine” treatment unit for treating patients. The position and orientation of the “handpiece” and/or “drill” as well as of a “mirror” can be measured in three-dimensional space with a 3-D measurement system. The system is intended to render three-dimensional images of a model jaw with teeth on a display and to represent the positions of the dental tool held by the student on the display relative to the image data of the phantom. It also has to compute and render the “image” of a dentist's mirror from the model data. It is also intended to shorten the time to train a dentist in the preparation of cavities. It should provide a sound and touch similar to that experienced when drilling a real tooth cavity. The device feeds backs to the student, so that the student can later in an actual treatment situation with a real patient and a real treatment tool properly interpret acoustic, tactile and visual information without navigation help and react accordingly. The student must drill a cavity in an artificial tooth of the phantom by taking into account a dental situation defined in the training concept. The compressed air supply to the pneumatic drive can be regulated with a valve, in order to give the student an acoustic and visual indication of the characteristics of a treatment situation. The power of the drill is reduced when simulating a hard tooth material, and is increased when simulating a soft tooth material. The controller follows in general the programmed geometric model characteristics of the simulated tooth model. For ergonomic reasons, the entire system can have the appearance of a dental treatment system. However, due to its concept and operating mode, the system cannot be used as a treatment system.
U.S. Pat. No. 5,257,203 describes a method for controlling a machine tool for, inter alia, dental modeling work. Such machines represents an excellent addition to the present invention. This machine, however, is not used with patients and is unable to later compensate for undercuts of the cavities on the patient.
U.S. Pat. No. 5,725,376 describes a method for producing drill templates. These methods have a significant disadvantage in that the drill template is difficult to affix on the mucous membrane of the mouth and a template for guiding the handpiece is placed exactly at the location where drilling occurs. The method can also not be used for producing cavities of arbitrary shape.
DE 19534590 A1 describes a method for ablation of hard tooth material. The laser power is hereby adjusted depending on the distance between the laser handpiece and the tissue. It is not possible to remove tissue with particular geometric characteristics.
DE 199 02 273 A1 describes a device for intra-operatively determining the placement of dental implants in the jawbone with a navigation system that can image the actual implant drilling position in a three-dimensional x-ray and can determine the spatial position with the help of an attached dynamic reference frame, characterized in that the dynamic reference frame consists of at least one fastening element on the teeth and/or the jaw and an associated releasable element with the dynamic reference frame. The method, however, was already in use in 1998 at the Charité and has been published.
U.S. Pat. No. 5,332,391 describes a device for supporting a plurality of dental handpieces, wherein each handpiece has a different angle of the drill axis relative to the normal orientation of the drill axis in the occlusion plane of the teeth, the device consisting of: a holder for guiding a dental handpiece, a connection in the form of a parallel structure with a free end on which a pivot point is secured for holding the orientation of the drill relative to the occlusion plane constant, and elements arranged next to the pivot point for connecting the holder with the pivot point, wherein the holder is detachable.
U.S. Pat. No. 5,989,024 describes an apparatus that cooperates with a driven tool with a longitudinal axis, whereby the apparatus holds the axis of the tool constant when the tool is moved in space, consisting of: an adjustable arm with two ends, a clamping arrangement for attaching the tool at one of the ends, a base at the other end, which can be secured to a workpiece, wherein the arm includes a first section that allows movement along the longitudinal axis of the tool.
U.S. Pat. No. 5,281,136 describes an apparatus for supporting a dental drill consisting of: a movable arm which can be affixed to a stationary reference point, and wherein the arm can be secured to an end of a dental drill, with the arm constructed so as to maintain the axis of the tool constant normal to a predefined work plane, components for stabilizing the head and the jaw of the patient, consisting of a head support which can be secured to a chair and elements for fixing the jaw on the head support.
U.S. Pat. No. 5,575,646 describes a device for supporting a dental drill consisting of: a support, an arm with two quadrilateral elements which are connected with each other in series while one of the quadrilateral elements is connected with the bearing and another with an element which holds a dental drill instrument, so that the axis of the drill instrument remains constant, an adjusting element for adjusting the direction of the work axis, wherein the bearing is provided with attachment elements for connection with the back support of a chair, wherein the quadrilateral elements are oriented with respect to each other at an angle of 90 degrees, so that one element is located above the patient and another in front of the patient.
U.S. Pat. No. 6,030,211 describes a guiding apparatus consisting of: a carriage which is secured at one point, an intermediate element, which is secured on one end on the carriage and can be moved in a first longitudinal coordinate z, and another end for receiving a connecting arm via an articulated joint, a working head disposed on the connecting arm and holding an instrument holder and two elements for moving the instrument holder along two additional longitudinal axes x and y, whereby the instrument holder is movable in x, y, z and a rotation axis.
WO98/40030 describes a system for transmitting the simulated position of dental implants from an x-ray machine to a robot which can be used to drill into an impression of the patient's jaw. The system includes a mechanical support as well as elements for fastening the impression on the support in a reproducible position. The impression includes at least two rectangular elements that are visible in an x-ray image.
The present state of the art offers no possibilities to provide the handpieces of the dentist at a later time with a marker when only small modifications are made, so that the handpieces can be easily used with a navigation system. Special handpieces exist for this application, which however have to be acquired by the dentist at a substantial cost. They cannot be used with normal turbines and the handpiece cannot be easily separated from the turbine.
Accordingly, the dentist has to have in inventory both “normal” and “navigatable” hand pieces.